As conventional memory cell structures approach scaling limits, other memory cell structures, such as resistive random access memory (RRAM) cells may enable increased miniaturization of electronic devices. Because of the simplicity of the RRAM cell, the RRAM cells may be used to make smaller devices having non-volatile memory characteristics and an inherently stable memory state.
Generally, an RRAM memory cell may include a variable resistor sandwiched between a first electrode and a second electrode. The variable resistor may be formed of a metal-doped glass material. When an electric field is applied to the metal-doped glass material, the metal ions diffuse within the glass to form a conductive bridge or a low resistance state. An electric field of opposite polarity may then be used to reset the cell to its original high resistance state by disbanding the conductive bridge.
Conventionally, to form the metal-doped glass material of the variable resistor, the glass material, such as a chalcogenide material, may be deposited followed by deposition of the metal material. The glass material and the metal material are subjected to a photo or thermal activation anneal to infuse the metal material into the glass material. However, such activation processes may damage components of the memory device previously formed, as well as increase the time required for forming the RRAM memory cell.
Silver-doped germanium sulfide is one example of a metal-doped glass material used in RRAM memory cells. The germanium sulfide can be deposited, for example, by physical vapor deposition (PVD), evaporation, or high temperature chemical vapor deposition, which are suitable methods for blanket deposition of the material. However, these methods do not enable the deposition of germanium sulfide in small openings. The silver can then be deposited by PVD or evaporation. The germanium sulfide and silver materials can then be subjected to photoactivation or thermal anneal, which can result in infusion of these materials.
Accordingly, additional methods of forming a variable resistor formed of a metal-doped chalcogenide material for use in a RRAM memory cell are needed.